Exemplary embodiments of the present invention relate to a semiconductor integrated circuit, and more particularly, to an interface apparatus of a semiconductor integrated circuit and an interfacing method thereof.
Recently designed semiconductor integrated circuits (ICs) require a high degree of integration, low power consumption, and a high operating speed. To fulfill these requirements, semiconductor integrated circuits are equipped with an interface apparatus for transmitting/receiving a signal/bar signal to/from an external circuit. Herein, the signal/bar signal includes a data signal and a data bar signal (that is, a logically inverted data signal), an address signal and an address bar signal (that is, a logically inverted address signal), and a command signal and a command bar signal (that is, a logically inverted command signal).
The interface apparatus of a semiconductor integrated circuit may include an input block having a plurality of receivers (Rx) each for receiving a signal or a bar signal from an external circuit. The interface apparatus of a semiconductor integrated circuit may also include an output block having a plurality of transmitters (Tx) each for transmitting a signal or a bar signal to the external circuit. The interface apparatus of a semiconductor integrated circuit may be bi-directional by including both an input block and an output block respectively having a plurality of receivers and transmitters. Generally, the input block, the output block, and the bi-directional structure including both an input block and an output block are arranged along with pads for simplifying design automation.
However, the interface apparatuses of conventional semiconductor integrated circuits including the output block and the bi-directional structure having both an input block and an output block have the following drawbacks.
When a voltage level VOX of a signal and a bar signal outputted by the output block are outside of a set range, a bit error may occur in an input block of an external circuit. Herein, “VOX” represents a voltage level of a cross point of the signal and the bar signal outputted by the output block.
Since no conventional technology provides a method for directly detecting the VOX, the VOX is indirectly detected by detecting jitter. When the VOX is converted into a time domain, it becomes jitter, and the fact that the cross point of a signal and a bar signal between a power source voltage VDD and a ground voltage VSS varies with a swing level indicates that a timing error has occurred. Therefore, when jitter is detected, the VOX is indirectly detected.
Conventional technologies use an oversampling method based on interpolation in order to detect jitter of a signal and a bar signal outputted by an output block. However, the conventional technologies have a drawback in that the interpolation and oversampling processes are too complicated to be simply realized in the output block. Moreover, since the output block characteristically occupies a large volume and since it includes a circuit having a high power consumption, the output path through which a data is outputted by the output block to an external circuit takes less time than an input path through which data is inputted from the input block to the internal circuitry of an integrated circuit. Therefore, it is difficult to add a circuit requiring a delay.
Consequently, it is desirable for a circuit for detecting the VOX to have a small volume, low power consumption and a short time delay.